ok - got zoom to work - another question

Wed Nov 24 08:53:30 PST 2004

Eric

Thanks for the help so far.

What am I trying to accomplish?

1) 1)  Learn how to do simple data display from my Mysql database to a map -
This I have achieved by coloring the polygons which represent where certain
teachers are by their zip code within California

2) Add zoom capability to my map so that users can zoom into a polygon ( or
zoom out ) - I have also achieved this

3) When user zooms into a colored polygon - I would like to put an ellipse
for each teacher in that polygon - This I have not achieved and I am having
no end of problems trying to achieve

Since this whole deal is a proof of concept type project so that we will get
the go-ahead for more advanced projects utilizing mapserver,  I would like
to do it as simply as possible.  I have been more-or-less working on my own
time to do this because I feel that it will be of great benefit to my shop.

I am very familiar with ArcView and ArcIMS  from installation to
modification and extension and I have found it be a bit painful to use -
little or no support for LAMP environments and very windows-centric and very
very costly.

I hope I have clarified my situation.  As far as data goes -

I have shape files of California with zip code data for the zip region
polygons.

Thanks again for putting up with me.

#Joseph Norris (Perl - what else is there?/Linux/CGI/Mysql) print @c=map chr
$_+100,(6,17,15,16,-68,-3,10,11,16,4,1,14,-68,12,1,14,8,-68,4,-3,-1,7,1,14,-
68,-26,11,15,1,12,4,-68,-22,11,14,14,5,15,-90);

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at lists.umn.edu]On
Behalf Of Eric Bridger
Sent: Wednesday, November 24, 2004 5:50 AM
To: MAPSERVER-USERS at lists.umn.edu
Subject: Re: [UMN_MAPSERVER-USERS] ok - got zoom to work - another question

On Tue, 2004-11-23 at 17:15, Joseph Norris wrote:
> Thanks Eric - so as I understand you:
>
> MAP
>   NAME CalMap
>   STATUS ON
>   EXTENT 5890870.385 -192053.200 8943310.847 3226086.749
>   IMAGETYPE GIF
>   SIZE 600 600
>   SHAPEPATH
>
"/usr/local/apache/htdocs/mco.communityservers.com/htdocs/maps/teacher/tdata
> "
>   IMAGECOLOR 255 255 255
>   TEMPLATEPATTERN "map"
>
>   SYMBOL
>     NAME 'circle'
>     TYPE ELLIPSE
>     POINTS 1 1 END
>     FILLED TRUE
>   END
>
>
>   LAYER
>     NAME "cal_zp_st"
>     TYPE POLYGON
>     DATA "cal_zp_st"
>     STATUS DEFAULT
>     CLASSITEM "ZCTA"
>
>     CLASS
>         EXPRESSION
>
/94087|90408|94107|95118|94530|74580|95404|93711|94904|92030|94121|91042|961
> 01|94523|95548|95658|92057|92503/
>       STYLE
>         SYMBOL 'circle'
>         SIZE 2
>         COLOR 255 102 102
>       END
>
>     END
>
>     CLASS
>       EXPRESSION /./
>       OUTLINECOLOR 204 204 204
>     END
>   END
>   LAYER
>     NAME "poly_minscale"
>     TYPE POLYGON
>     DATA "cal_zp_st"
>     STATUS DEFAULT
>     MINSCALE ????
>     CLASS
>      SYMBOL 'circle'
>       SIZE 2
>       COLOR 255 102 102
>      END
>   END
>      LAYER
>     NAME "poly_maxscale"
>     TYPE POLYGON
>     DATA "cal_zp_st"
>     STATUS DEFAULT
>     MAXSCALE????
>  I don't know what the class would be if any
>   END
>
>
> END # end map from header
>
> How do I determine the minscale and maxscale?
>
> Thanks
>
> #Joseph Norris (Perl - what else is there?/Linux/CGI/Mysql) print @c=map
chr
>
$_+100,(6,17,15,16,-68,-3,10,11,16,4,1,14,-68,12,1,14,8,-68,4,-3,-1,7,1,14,-
> 68,-26,11,15,1,12,4,-68,-22,11,14,14,5,15,-90);
>
> -----Original Message-----
> From: UMN MapServer Users List [mailto:MAPSERVER-USERS at lists.umn.edu]On
> Behalf Of Eric Bridger
> Sent: Monday, November 22, 2004 9:53 AM
> To: MAPSERVER-USERS at lists.umn.edu
> Subject: Re: [UMN_MAPSERVER-USERS] ok - got zoom to work - another
question
>
> At 08:39 AM 11/22/2004 -0800, Joseph Norris wrote:
> >Everyone,
> >
> >I have my zoom working but now I would like to tackle something else.  I
am
> >putting an ellipse in the zip polygons if there is a 1-more teachers
there.
> >For each zip there maybe a max of 10 teachers.  I would like an ellipse
or
> >symbol for each one so that when the user zooms into the polygon they can
> >see a symbol for each teacher. Can I do this within the class?  If so how
> or
> >would be the best way to handle this?
>
>
> You can do this in the map file by creating two layers and using MAXSCALE,
> MINSCALE.
> Layer 1 has one ellipse per zip wherever there are 1-10 teachers.
> MINSCALE is set so that it won't appear when you are zoomed in.
> Layer 2 has one ellipse for each teacher and has MAXSCALE set so that it
> turns on when Layer 1 is turned off.
>
> Of course if you are using Perl Mapscript you will need to calculate the
> scale yourself and turn on and off the layers yourself.
> Here's and example:
>
> my $current_scale = calculateScale($map, $imgext[0], $imgext[2]);
> # From mapserver3.6.4: mapscale.c msCalculateScale().  This is not a
> precision thing. We don't worry about
> # msAdjustExtent() since in all our maps, image SIZE has same aspect ratio
> as the map EXTENT.
> # $minx and $maxx are optional in which case the current extent of the map
> is used.
>
> # Be careful about the current map's extent. zoomMap() changes the
extents.
>
> sub calculateScale{
>     my ($map, $minx, $maxx) = @_;
>     if(!$minx){
>         $minx = $map->{extent}->{minx};
>         $maxx = $map->{extent}->{maxx};
>     }
>     my @inchesPerUnit = (1, 12, 63360.0, 39.3701, 39370.1, 4374754);
>     my $width = $map->{width};
>     my $units = $map->{units}; # index into unitsPerUnit array
>     my $resolution = $map->{resolution};
>     my $md = $width / ($resolution * $inchesPerUnit[$units]);
>     my $gd = $maxx - $minx;
>     return($gd/$md);
> }

Joseph,
I'm not exactly sure what your data looks like or what you are trying to
achieve. But by using two layers you can control what exactly is
displayed via different CLASS and EXPRESSION's at different scales.

The scale is determined by the current map's extents, (AFTER any zooming
in which you calculated new extents based on the zoom direction.

(Actually this call:
my $current_scale = calculateScale($map, $imgext[0], $imgext[2]);
gets the scale of the map which was just submitted, based on:
  @imgext = split(' ', $q->param('imgext')); where imgext is the extent
just submitted with the form.)

Typically you'd want to call $scale = calculateScale($map) (after your
zoom calculations have changed the map's extents.

What MIXSCALE, MAXSCALE to use in your map file must be determined by
trail and error.

HTH.
Eric